在一个查询中组合多个sql / mysql查询

Question

I have 5 tables. Namely user, reference_1, reference_2, reference_3 and question

user => (user_id,user_name,user_emailid,user_mobno)
reference_1 => (ref_id_1,user_id,ref_name,ref_email,ref_mobno)
reference_2 => (ref_id_2,user_id,ref_name,ref_email,ref_mobno)
reference_3 => (ref_id_3,user_id,ref_name,ref_email,ref_mobno)
question => (que_id,user_id,ref_id_1,ref_id_2,ref_id_3,que1_name,que2_name,que3_name,que4_name,que5_name,que6a_name,que6b_name,que7_name,qa1,qa2,qa3,qa4,qa5,qa6a,qa6b,qa7,flag)

I fired 4 consecutive queries:

Query 1: Fetching the data from the user table and question using a LEFT JOIN

select u.user_name,u.user_emailid,u.user_mobno,
  q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7
from user u
LEFT JOIN question q
on u.user_id = q.user_id
WHERE q.flag = 1

Query 2: Fetching the data from the user table and reference_1 using LEFT JOIN

select r1.ref_name,r1.ref_email,r1.ref_mobno,
  q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7
from reference_1 r1
left join question q
on r1.ref_id_1 = q.ref_id_1

Query 3: Fetching the data from the user table and reference_2 using LEFT JOIN

select r2.ref_name,r2.ref_email,r2.ref_mobno,  
  q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.que6a_nam e,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7
from reference_2 r2
left join question q
on r2.ref_id_2 = q.ref_id_2

Query 4: Fetching the data from the user table and reference_3 using LEFT JOIN

select r3.ref_name,r3.ref_email,r3.ref_mobno,  
  q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7
from reference_3 r3
left join question q
on r3.ref_id_3 = q.ref_id_3

Now there is a requirement to combine all 4 queries in one to show the data.

I tried JOIN all these queries in one query

select u.user_name,u.user_emailid,u.user_mobno,

q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7,

r1.ref_name,r1.ref_email,r1.ref_mobno,  q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7,

r2.ref_name,r2.ref_email,r2.ref_mobno,  q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7,

r3.ref_name,r3.ref_email,r3.ref_mobno, q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7

from user u
LEFT JOIN question q
on u.user_id = q.user_id
WHERE q.flag = 1
LEFT JOIN reference_1 r1
LEFT JOIN question q1
on r1.ref_id_1 = q1.ref_id_1
LEFT JOIN reference_2 r2
LEFT JOIN question q2
on r2.ref_id_2 = q2.ref_id_2
LEFT JOIN reference_3 r3
LEFT JOIN question q3
on r3.ref_id_3 = q3.ref_id_3

But this query is not working.

Answer 1

Because you screwed syntax order...

Multi join works like this:

select u.user_name,u.user_emailid,u.user_mobno,     q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.    que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7,

r1.ref_name,r1.ref_email,r1.ref_mobno,   q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.    que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7,

r2.ref_name,r2.ref_email,r2.ref_mobno,  q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.    que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7,

r3.ref_name,r3.ref_email,r3.ref_mobno, q.que1_name,q.qa1,q.que2_name,q.qa2,q.que3_name,q.qa3,q.que4_name,q.qa4,q.que5_name,q.qa5,q.    que6a_name,q.qa6a,q.que6b_name,q.qa6b,q.que7_name,q.qa7

from question q
LEFT JOIN user u USING(user_id)
LEFT JOIN reference_1 r1 USING(ref_id_1)
LEFT JOIN reference_2 r2 USING(ref_id_2)
LEFT JOIN reference_3 r3 USING(ref_id_3)
WHERE q.flag = 1

Where must be at the end... Joins must be stated completely and cannot be mixed. Order in dependency works you can have sub and subsub and so on dependencies without a problem.

One thing you did pretty good: You set-up same name for foreign key in both JOIN tables. In this case you can simply replace r1.t1 = r2.t2 stuff and just define the join table in function USING(t1). :)